Diaphragm operated water valves of the type shown herein are well understood in the art. The center vent hole is customarily made as small as possible to minimize the actuating forces required and, therefore, to reduce the size and expense of the solenoid coil. The bleed hole must be smaller than the pilot hole to insure that the pressure differentials developed across the diaphragm will provide the valve opening and closing function. A typical bleed hole for water valves of the type used in clothes washing machines and the like is 0.030 inches.
These valves are used in domestic water systems and such systems frequently have particles entrained in the water supply. A particle the size of the bleed hole will close off the bleed hole and cause malfunction. If the bleed hole size is increased, sticking of the armature (valve) is likely becuase the larger particles passed through the bleed hole get wedged between the armature and the guide. If the bleed hole is made smaller, a higher incidence of plugged bleed holes occurs due to the vulnerability of a small bleed hole to a wider range of particle sizes.
To minimize the effect of particles in the water, filter screens are mounted in the inlet but if the screen is too fine it constitutes too great a flow restriction. The customary practice today incorporates a rigid plastic insert in which the bleed hole is located. In an effort to restrict access of particles to the bleed hole, one current design employs a multiplicity of holes leading to a conduit in the plastic insert and the conduit leads to the bleed hole. Thus a number of the first holes can become plugged without plugging the actual bleed hole. This design, however, is somewhat costly and is subject to plugging by a finite number of particles, i.e., one per primary hole, and there is little opportunity for this design to, in effect, be self-cleaning to thereby prolong the service life of the valve.
This invention is directed to reducing or eliminating valve failure by reason of plugging the bleed hole.